Use & Application Of Oxygen Isotopes In Ground Water Studies
Introduction
- Naturally occurring oxygen is composed of three stable isotopes 16O, 17O, and 18O.
- 16O being the most abundant (99.762% natural abundance)
- Known oxygen isotopes range in mass number from 12 to 24.
- 16O is a primary isotope while 17O and 18O are secondary isotopes
Biological Oxygen Demand (BOD)Stable oxygen is used in
- ground water studies
- to investigate recharge,
- ground water interaction
- surface water interaction
- Paleo hydrogeologic interactions
- to estimate ground water ages
Paleoclimatology
The ratio of 18O to 16O in ice and deep sea cores is temperature dependent
Thus, can be used as a proxy measure for reconstructing climate change.
During colder periods,16O is preferentially evaporated , leaving the slightly heavier and more sluggish 18O behind.
Factors affecting
GLOBAL PROCESSES
(i) Temperature change effects
Dansgard (1964) plotted the relationship between temperature (taken as the mean annual air temperature for a station) and the δ18O value.
From this he derived the graph and equation
Graph clearly shows the very strong relationship between temperature and δ18O.
This is a response to greater fractionation taking place at low temperatures than at high temperatures
LOCAL PROCESSES
(i) Altitude effects Temperature decreases with altitude. This is again a temperature driven effect.
CONCLUSION
Thus, oxygen isotopes play a major role in ground water studies which may be helpful for further researches. Its temprature dependency plays key role in its importance.